The present invention relates generally to load carrying devices. More particularly, it relates to shock absorbing devices of the type which are mounted to vehicles and which use both an elastomeric spring and a selectively pressurizable chamber for absorbing shock, energy dissipation and carrying and leveling load. However, it will be appreciated by those skilled in the art that the invention can be readily adapted for use in other environments as, for example, where similar spring damping devices are employed to protect or cushion other items.
Known dry viscous spring damper devices of the type described have included elastomeric shear springs, elastomeric diaphragms, selectively pressurizable gas chambers and subchambers including elastomeric composite particles or fluid. Such a dry viscous spring damper device is described in application Ser. No. 436,331, filed Oct. 25, 1982, now U.S. Pat. No. 4,504,044 in the name of Shtarkman and assigned to the assignee of the subject application. In the Shtarkman application a dry viscous spring damper is provided which is comprised of a first housing member joined to a second housing member with an elastomeric shear spring. A first chamber in the damper is separated from a second chamber in the damper by an elastomeric diaphragm. A valve is provided for selectively pressurizing the second chamber with pressurized gas or air. A plurality of elastomeric particles are included in the first chamber whereby relative movement between the housing members operates to stress the shear spring and the elastomeric particles and vary the volumes of the first and second chambers.
A particular problem with viscous spring dampers is the lack of effective control over the form of deformation of the springs of such devices. Where a shear stress compels a spring into frictional engagement with a contiguous rigid member, the friction wears away the spring to shorten its life and weaken it. In addition, such frictional engagement limits the natural deformation of the spring to affect its operation.
Another particular problem with prior spring dampers is damper responsive instability due to nonaxial vibration, loading and deformation. Such nonaxial deformation may comprise conical twisting or rotation of the respective housing members to a different degree about the axis of the damper. Such instability is enhanced particularly where the damper is loaded to a substantially commpressed state which imparts high shear forces to the elastomeric shear spring.
Spring struts are load supporting devices which absorb shock and dissipate energy but are primarily limited to absorbing dissipation in a single axial dimension only. A rigid structural member bears side or nonaxial forces. Accordingly, nonaxial deformation is generally not present in a strut.
The present invention comprises a new and improved device which overcomes the energy absorption and frictional deformation problems of prior dry viscous spring dampers by combining the advantageous features of a dry viscous spring damper with structural means for generally limiting deformation of the device in an axial direction only and by providing surfaces contiguous to the strut shear springs to allow nonfrictional deformation. The subject invention is simple in design, economical to manufacture, readily adaptable to a plurality of energy dissipation uses, and provides improved shock absorption and energy dissipation.